Quick answer
CO₂-equivalent = mass × GWP₁₀₀. Carbon dioxide has a GWP of 1, so 100 kg of CO₂ is 100 kg CO₂e; methane has a 100-year GWP of roughly 28 to 30, so 100 kg of methane is about 2,800 to 3,000 kg CO₂e.
Choose a gas and enter the mass emitted. The calculator returns the CO₂ equivalent. Use this greenhouse gas conversion calculator to check your own figures.
Related tools: Electricity Emissions Calculator: CO₂ from electricity use at an emission factor you enter. Fuel Emissions Calculator: CO₂ from burning gasoline or diesel. Travel Emissions Calculator: CO₂ from a trip at an emission factor you enter.
How to use the Greenhouse Gas Conversion Calculator
- Choose gas: Carbon dioxide (GWP 1), Methane (GWP 28) and Nitrous oxide (GWP 265).
- Enter mass emitted (kg) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Gas | Choose one: Carbon dioxide (GWP 1); Methane (GWP 28); Nitrous oxide (GWP 265) | Starts at Methane (GWP 28) |
| Mass emitted | A number, in kg | > 0 |
Formula and method
Formula
CO₂e = mass × GWP₁₀₀
IEEE-754 double precision; shown to the decimals indicated.
Uses IPCC Fifth Assessment Report 100-year values without climate–carbon feedbacks (CH₄ 28, N₂O 265); other reports use different values.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Gas = Carbon dioxide (GWP 1); Mass emitted = 100.
| Result | Value |
|---|---|
| CO₂ equivalent | 100 kg CO₂e |
Example 2
Inputs: Gas = Methane (GWP 28); Mass emitted = 10.
| Result | Value |
|---|---|
| CO₂ equivalent | 280 kg CO₂e |
Example 3
Inputs: Gas = Nitrous oxide (GWP 265); Mass emitted = 2.
| Result | Value |
|---|---|
| CO₂ equivalent | 530 kg CO₂e |
The first line is the headline result (cO₂ equivalent). IEEE-754 double precision; shown to the decimals indicated.
Why GWP
Global warming potential compares how much heat a gas traps over 100 years relative to CO₂. Nitrous oxide is about 265 to 273 and some refrigerants run into the thousands.
Report differences
GWP values differ between IPCC assessment reports (AR4, AR5, AR6), so state which you use. Methane's short life makes the choice of 20- versus 100-year horizon matter.
How the result changes with mass emitted
Holding every other input at the first worked example, this table changes only mass emitted. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Mass emitted | CO₂ equivalent |
|---|---|
| 50 | 50 kg CO₂e |
| 100 | 100 kg CO₂e |
| 200 | 200 kg CO₂e |
| 400 | 400 kg CO₂e |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Mass emitted: entering "0" shows "Mass emitted must be greater than 0." beside that field and no result.
Choosing between the Greenhouse Gas Conversion Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Electricity Emissions Calculator](/science/electricity-emissions-calculator/) | electricity used and emission factor | CO₂ emitted |
| [Fuel Emissions Calculator](/science/fuel-emissions-calculator/) | fuel and fuel burned | CO₂ emitted |
| [Travel Emissions Calculator](/science/travel-emissions-calculator/) | distance traveled and emission factor | CO₂ emitted |
| [Scale Conversion Calculator](/converters/scale-conversion/) | scale denominator N, convert and length | Converted length |
| [Butter Conversion Calculator](/cooking/butter-conversion-calculator/) | i have and amount | Butter |
Background: environment and acoustics
Decibels are a logarithmic scale, so sound levels cannot be added arithmetically: two equal sources raise the level by about 3 dB, not double it. Environmental and emissions results depend on the factors behind them (for example the US EPA's equivalency factors), which are averages for a country, fuel and year.
Use the result to compare scenarios rather than as a measured value.
Assumptions and limitations
- GWP values differ between assessment reports
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for mass emitted to confirm this.
Frequently asked questions
What is CO₂e?
The CO₂ amount with the same warming effect.
Why does methane matter?
It traps more heat per kg.
Which report should I use?
Whatever your reporting standard specifies.
What does the Greenhouse Gas Conversion Calculator calculate?
Convert methane or nitrous oxide to CO₂ equivalent (100-year GWP). It returns CO₂ equivalent.
What formula does the Greenhouse Gas Conversion Calculator use?
CO₂e = mass × GWP₁₀₀. Uses IPCC Fifth Assessment Report 100-year values without climate–carbon feedbacks (CH₄ 28, N₂O 265); other reports use different values.
What do I need to enter in the greenhouse Gas Conversion Calculator?
You enter Gas and Mass emitted (kg).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. GWP values differ between assessment reports.
What does the “Gas” option change?
It sets how the greenhouse Gas Conversion is worked out. The choices are Carbon dioxide (GWP 1), Methane (GWP 28) and Nitrous oxide (GWP 265).
What is an example of a greenhouse Gas Conversion result?
With gas Carbon dioxide (GWP 1) and mass emitted 100, the cO₂ equivalent is 100 kg CO₂e.
Where does the method come from?
The method follows: IPCC AR5 WG1, Chapter 8, Table 8.7.
Related calculators
- Electricity Emissions Calculator — CO₂ from electricity use at an emission factor you enter.
- Fuel Emissions Calculator — CO₂ from burning gasoline or diesel.
- Travel Emissions Calculator — CO₂ from a trip at an emission factor you enter.
- Scale Conversion Calculator — Convert between model and actual lengths at a 1:N scale.
- Conversion Rate Calculator — Share of visitors who convert.
Sources
- IPCC AR5 WG1, Chapter 8, Table 8.7
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.